[BUGFIX] Modify SQL Server IDENTITY_INSERT when creating records

In SQL Server (MSSQL), hard setting uid auto-increment primary keys is
only allowed if the table is prepared for such an operation beforehand.

When executing functional test cases a new database connection wrapper
is invoked, which automatically modifies IDENTITY_INSERT in case the
use database platform is SQL Server.

Classes/Core/DatabaseConnectionWrapper.php

@@ -0,0 +1,92 @@
+<?php
+declare(strict_types=1);
+namespace TYPO3\TestingFramework\Core;
+
+/*
+ * This file is part of the TYPO3 CMS project.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ *
+ * For the full copyright and license information, please read the
+ * LICENSE.txt file that was distributed with this source code.
+ *
+ * The TYPO3 project - inspiring people to share!
+ */
+
+use TYPO3\CMS\Core\Database\Connection;
+
+/**
+ * Wrapper for database connections in order to intercept statement executions.
+ */
+class DatabaseConnectionWrapper extends Connection
+{
+    /**
+     * Wraps insert execution in order to consider SQL Server IDENTITY_INSERT.
+     *
+     * @param string $tableName
+     * @param array $data
+     * @param array $types
+     * @return int
+     */
+    public function insert($tableName, array $data, array $types = []): int
+    {
+        $modified = $this->modifyServerIdentity($tableName, true);
+
+        $result = parent::insert($tableName, $data, $types);
+
+        if ($modified) {
+            $this->modifyServerIdentity($tableName, false);
+        }
+
+        return $result;
+    }
+
+
+    /**
+     * In SQL Server (MSSQL), hard setting uid auto-increment primary keys is
+     * only allowed if the table is prepared for such an operation beforehand.
+     * This method has to be invoked explicitly before INSERT statements in
+     * order to enable the behavior and has to be disabled afterwards again.
+     *
+     * Quotation of SQL Server SET IDENTITY_INSERT (Transact-SQL) documentation:
+     * > At any time, only one table in a session can have the IDENTITY_INSERT
+     * > property set to ON. If a table already has this property set to ON,
+     * > and a SET IDENTITY_INSERT ON statement is issued for another table,
+     * > SQL Server returns an error message that states SET IDENTITY_INSERT
+     * > is already ON and reports the table it is set ON for.
+     *
+     * @param string $tableName Table name to be modified
+     * @param bool $enable Whether to enable ('ON') or disable ('OFF')
+     * @return bool Whether executed statement has be successful
+     */
+    private function modifyServerIdentity(string $tableName, bool $enable): bool
+    {
+        try {
+            $platform = $this->getDatabasePlatform();
+        } catch (DBALException $exception) {
+            return false;
+        }
+
+        if (!$platform instanceof SQLServerPlatform) {
+            return false;
+        }
+
+        try {
+            $statement = sprintf(
+                'SET IDENTITY_INSERT %s %s',
+                $tableName,
+                $enable ? 'ON' : 'OFF'
+            );
+            $this->exec($statement);
+            return true;
+        } catch (DBALException $e) {
+            // Some tables like sys_refindex don't have an auto-increment uid field and thus no
+            // IDENTITY column. Instead of testing existance, we just try to set IDENTITY ON
+            // and catch the possible error that occurs.
+        }
+
+        return false;
+    }
+}

Classes/Core/Functional/FunctionalTestCase.php

@@ -24,6 +24,7 @@
 use TYPO3\CMS\Core\Database\ConnectionPool;
 use TYPO3\CMS\Core\Utility\GeneralUtility;
 use TYPO3\TestingFramework\Core\BaseTestCase;
+use TYPO3\TestingFramework\Core\DatabaseConnectionWrapper;
 use TYPO3\TestingFramework\Core\Exception;
 use TYPO3\TestingFramework\Core\Functional\Framework\DataHandling\DataSet;
 use TYPO3\TestingFramework\Core\Functional\Framework\Frontend\InternalRequest;
@@ -288,6 +289,7 @@ protected function setUp()
                 // Append the unique identifier to the base database name to end up with a single database per test case
                 $dbName = $originalDatabaseName . '_ft' . $this->identifier;
                 $localConfiguration['DB']['Connections']['Default']['dbname'] = $dbName;
+                $localConfiguration['DB']['Connections']['Default']['wrapperClass'] = DatabaseConnectionWrapper::class;
                 $testbase->testDatabaseNameIsNotTooLong($originalDatabaseName, $localConfiguration);
             } else {
                 $dbPath = $this->instancePath . '/test.sqlite';